Fix org ruleset workflow to reference reusable workflow from security-github-actions repo

- Changed from local reference (./.github/workflows/reusable-trufflehog.yml)
- To remote reference (grafana/security-github-actions/.github/workflows/reusable-trufflehog.yml@main)
- This allows org rulesets to work properly across target repositories

Author: isaiah-grafana

.github/workflows/org-required-trufflehog.yml

@@ -18,7 +18,7 @@ permissions:
 jobs:
   secret-scan:
     name: TruffleHog Secret Scan
-    uses: ./.github/workflows/reusable-trufflehog.yml
+    uses: grafana/security-github-actions/.github/workflows/reusable-trufflehog.yml@main
     with:
       # Monitoring mode - no blocking, just reporting
       fail-on-verified: "false"      # Don't block on verified secrets (monitoring only)